Editing Octopus (section)

==Behaviour and ecology==

Octopuses are mostly solitary<ref name=Mather/>{{rp|17, 134}} though a few are known to live in groups and interact regularly, usually in the context of [[Dominance hierarchy|dominance]] and reproductive competition. This is likely the result of abundant food supplies combined with fewer den sites.<ref>{{cite journal |last=Scheel |first=D. |display-authors=etal |year=2017 |title=A second site occupied by ''Octopus tetricus'' at high densities, with notes on their ecology and behavior |journal=Marine and Freshwater Behaviour and Physiology |volume=50 |issue=4 |pages=285–291 |doi=10.1080/10236244.2017.1369851 |bibcode=2017MFBP...50..285S |s2cid=89738642}}</ref> The [[Larger Pacific striped octopus]] has been described as particularly social, living in groups of up to 40.<ref>{{cite journal |last=Rodaniche |first=Arcadio F. |date=1991 |title=Notes on the behavior of the Larger Pacific Striped Octopus, an undescribed species of the genus Octopus |journal=Bulletin of Marine Science |volume=49 |pages=667}}</ref><ref>{{cite journal |last1=Caldwell |first1=Roy L. |last2=Ross |first2=Richard |last3=Rodaniche |first3=Arcadio |last4=Huffard |first4=Christine L. |year=2015 |title=Behavior and Body Patterns of the Larger Pacific Striped Octopus |journal=PLOS ONE |volume=10 |issue=8 |pages=e0134152 |doi=10.1371/journal.pone.0134152 |issn=1932-6203 |pmc=4534201 |pmid=26266543 |bibcode=2015PLoSO..1034152C|doi-access=free }}</ref> Octopuses hide in dens, which are typically crevices in rocky or other hard structures, including man-made ones. Small species may use abandoned shells and bottles.<ref name=Mather/>{{rp|69, 74–75}}  They can [[Animal navigation|navigate]] to a den without having to retrace their outward route.<ref>{{cite journal |url=https://blogs.scientificamerican.com/thoughtful-animal/how-do-octopuses-navigate/ |title=How do octopuses navigate? |last=Goldman |first=Jason G. |date=24 May 2012 |journal=Scientific American |volume=168 |issue=4 |pages=491–497 |doi=10.1007/BF00199609 |s2cid=41369931 |access-date=8 June 2017}}</ref> They are not migratory.<ref name=Courage/>{{rp|45–46}}

Octopuses bring captured prey to the den to eat. Dens are often surrounded by a [[midden]] of dead and uneaten food items. These middens may attract scavengers such as fish, molluscs, and [[echinoderm]]s.<ref name=Crowfootfeeding>{{cite web |url=http://www.asnailsodyssey.com/LEARNABOUT/OCTOPUS/octoFeed.php |title=Octopuses and Relatives: Feeding, diets and growth |last=Carefoot |first=Thomas |work=A Snail's Odyssey |access-date=13 April 2017 |archive-url=https://web.archive.org/web/20170508060739/http://www.asnailsodyssey.com/LEARNABOUT/OCTOPUS/octoFeed.php |archive-date=8 May 2017 |url-status=dead}}</ref> On rare occasions, octopuses [[interspecific cooperation|hunt cooperatively with other species]], with fish as their partners. They regulate the [[species composition]] of the hunting {{nowrap|group{{tsp}}{{mdash}}}}{{tsp}}and the behavior of their {{nowrap|partners{{tsp}}{{mdash}}}}{{tsp}}by punching them.<ref name="Sampaio 2020">{{cite journal |last1=Sampaio |first1=Eduardo |last2=Seco |first2=Martim Costa |last3=Rosa |first3=Rui |last4=Gingins |first4=Simon |title=Octopuses punch fishes during collaborative interspecific hunting events |journal=[[Ecology (journal)|Ecology]] |publisher=[[Ecological Society of America]]/[[Wiley Publishing]] |date=18 December 2020 |volume=102 |issue=3 |pages=e03266 |issn=0012-9658 |doi=10.1002/ecy.3266 |pmid=33338268 |doi-access=free}}</ref>

===Feeding===
[[File:Veined Octopus - Amphioctopus Marginatus eating a Crab.jpg|thumb|left|[[Amphioctopus marginatus|Veined octopus]] eating a crab|alt=An octopus in an open seashell on a sandy surface, surrounding a small crab with the suckers on its arms]]

Octopuses are generally predatory and feed on prey such as [[crustacean]]s, [[Bivalvia|bivalves]], [[gastropod]]s, fish, and other cephalopods, including [[cannibalism|members of the same species]].<ref name=Hanlon>{{cite book |title=Cephalopod Behaviour |publisher=Cambridge University Press |last1=Hanlon |first1=R. T. |last2=Messenger |first2=J. B. |year=1998 |edition=1st|isbn=0-521-64583-2}}</ref>{{rp|47, 60}} Major items in the diet of the giant Pacific octopus include bivalves such as the cockle ''[[Clinocardium nuttallii]]'', clams and scallops and crustaceans such as [[crab]]s. It typically rejects [[Naticidae|moon snails]] because they are too large; [[limpet]]s, [[Crassadoma|rock scallops]], [[chiton]]s and [[abalone]], because they are too securely fixed to the rock.<ref name=Crowfootfeeding/> Small cirrate octopuses such as those of the genera ''[[Grimpoteuthis]]'' and ''[[Opisthoteuthis]]'' typically prey on polychaetes, [[copepod]]s, [[amphipod]]s and [[isopod]]s.<ref name=":9">{{Cite book |last1=Collins |first1=Martin A. |last2=Villanueva |first2=Roger |date=2006 |chapter=Taxonomy, ecology and behaviour of the cirrate octopods |title=Oceanography and Marine Biology: An Annual Review |volume=44 |pages=277–322 |doi=10.1201/9781420006391.ch6 |doi-broken-date=12 November 2024 |chapter-url=https://www.researchgate.net/publication/266220687 |access-date=5 February 2024 |isbn=978-0-8493-7044-1}}</ref>

Octopuses typically locate prey by feeling through their environment;<ref name=Mather/>{{rp|60}} some species hide and ambush their target.<ref name=Hanlon/>{{rp|54}} When prey tries to escape, the octopus jets after it.<ref name=Mather/>{{rp|61}} Octopuses may drill into the shells of crustaceans, bivalves and gastropods. It used to be thought that drilling was done by the radula, but it has now been shown that minute teeth at the tip of the salivary papilla are involved, and an enzyme in the toxic saliva is used to dissolve the calcium carbonate of the shell. This can take hours and once the shell is penetrated, the prey dies almost instantaneously. With crabs, tough-shelled species are more likely to be drilled, and soft-shelled crabs are torn apart.<ref name=Crowfoothandling>{{cite web |url=http://www.asnailsodyssey.com/LEARNABOUT/OCTOPUS/octoHand.php |title=Octopuses and Relatives: Prey handling and drilling |last=Carefoot |first=Thomas |work=A Snail's Odyssey |access-date=21 April 2017 |archive-url=https://web.archive.org/web/20170606005247/http://www.asnailsodyssey.com/LEARNABOUT/OCTOPUS/octoHand.php |archive-date=6 June 2017 |url-status=dead }}</ref>

Some species have other modes of feeding. ''[[Grimpoteuthis]]'' either lacks or has a small radula and swallows prey whole.<ref name="marinebio"/> In the deep-sea genus ''[[Stauroteuthis]]'',  the suckers in most species have been altered into [[photophore]]s which are believed to fool prey by directing them to the mouth, making them one of the few [[bioluminescent]] octopuses.<ref>{{cite journal |doi=10.2307/1542994 |pmid=28296499 |last1=Johnsen |first1=S. |first2=E. J. |last2=Balser |first3=E. C. |last3=Fisher |first4=E. A. |last4=Widder |year=1999 |url=http://www.biology.duke.edu/johnsenlab/pdfs/pubs/octopusbiolbull.pdf |title=Bioluminescence in the deep-sea cirrate octopod ''Stauroteuthis syrtensis'' Verrill (Mollusca: Cephalopoda) |journal=The Biological Bulletin |volume=197 |issue=1 |pages=26–39 |url-status=dead |archive-url=https://web.archive.org/web/20110305114611/http://www.biology.duke.edu/johnsenlab/pdfs/pubs/octopusbiolbull.pdf |archive-date=5 March 2011  |jstor=1542994 }}</ref>

===Locomotion===
[[File:Octopus3.jpg| thumb|right|Octopuses swim with their arms trailing behind.|alt=An octopus swimming with its round body to the front, its arms forming a streamlined tube behind]]
Octopuses mainly move about by relatively slow crawling with some swimming in a head-first position. [[Jet propulsion]] or backward swimming, is their fastest means of locomotion, while crawling is slowest.<ref name="biologists2006">{{cite journal |first=Christine L. |last=Huffard |title=Locomotion by ''Abdopus aculeatus'' (Cephalopoda: Octopodidae): walking the line between primary and secondary defenses |journal=Journal of Experimental Biology |year=2006 |volume=209 |issue=Pt 19 |pages=3697–3707 |doi=10.1242/jeb.02435 |pmid=16985187| doi-access=free |bibcode=2006JExpB.209.3697H }}</ref> While crawling, the suckers adhere and detach from the substrate as the animal hauls itself forward with its powerful arm muscles.<ref name=Crowfootcrawling/><ref name="biologists2006"/> In 2005, ''[[Abdopus|Adopus aculeatus]]'' and veined octopus (''[[Amphioctopus marginatus]]'') were found to walk on two arms, while at the same time mimicking plant matter.<ref>{{cite journal |doi=10.1126/science.1109616 |title=Underwater Bipedal Locomotion by Octopuses in Disguise |year=2005 |last1=Huffard |first1=C. L. |journal=Science |volume=307 |issue=5717 |page=1927 |pmid=15790846 |last2=Boneka |first2=F. |last3=Full |first3=R. J. |s2cid=21030132 }}</ref> This form of locomotion allows these octopuses to move quickly away from a potential predator without being recognised.<ref name="biologists2006"/> Some species of octopus can crawl out of the water briefly, which they may do between tide pools.<ref name="Wood Anderson"/><ref name=Mather/>{{rp|183}} "Stilt walking" is used by the veined octopus when carrying stacked coconut shells. The octopus carries the shells underneath it with two arms, and progresses with an awkward gait supported by its remaining arms, which are stiffened.<ref name=Finn/>
[[File:Cirroteuthis muelleri NOAA.jpg|thumb|upright=1.5<!--width for low aspect ratio image-->|Movements of the finned species ''[[Cirroteuthis muelleri]]''|alt=Three images in sequence of a two-finned sea creature swimming with an eight-cornered web]]
Most octopuses swim by expelling a jet of water from the mantle through the siphon into the sea. The direction of travel depends on the orientation of the siphon. When swimming, the head is at the front and the siphon is pointed backward but, when jetting, the visceral hump leads, the siphon points at the head and the arms trail behind, with the animal presenting a [[Spindle (textiles)|fusiform]] appearance. In an alternative method of swimming, some species flatten themselves dorso-ventrally, and swim with the arms splayed; this may provide lift and be faster than normal swimming. Jetting is used to escape from danger, but is physiologically inefficient, requiring a mantle pressure so high as to stop the heart from beating, resulting in a progressive oxygen deficit.<ref name="biologists2006"/>

Cirrate octopuses cannot produce jet propulsion and swim using their fins. Their neutrally buoyant bodies float along while the fins are spread. They can also contract their arms and surrounding web to make sudden moves known as "take-offs". Another form of locomotion is "pumping", which involves symmetrical contractions of muscles in their webs producing [[peristalsis|peristaltic waves]], moving them slowly.<ref name="marinebio"/>

===Intelligence===
{{Main |Cephalopod intelligence}}

[[File:Oktopus opening a container with screw cap 02 (cropped).jpg|thumb|upright|Octopus opening a container by unscrewing its cap|alt=A captive octopus with two arms wrapped around the cap of a plastic container]]

Octopuses are highly [[intelligence|intelligent]].<ref name="doug">{{cite journal |url=https://www.nwf.org/Magazines/National-Wildlife/1997/Armed-But-Not-Dangerous |title=Armed but not dangerous: Is the octopus really the invertebrate intellect of the sea |first=Doug |last=Stewart |journal=National Wildlife |year=1997 |volume=35 |issue=2}}</ref> [[Maze]] and [[problem solving|problem-solving]] experiments have shown evidence of a memory system that can store both [[short-term memory|short-]] and [[long-term memory]].<ref name="Zarrella Ponte Baldascino Fiorito 2015">{{cite journal |last1=Zarrella |first1=Ilaria |last2=Ponte |first2=Giovanna |last3=Baldascino |first3=Elena |last4=Fiorito |first4=Graziano |title=Learning and memory in Octopus vulgaris: a case of biological plasticity |journal=Current Opinion in Neurobiology |volume=35 |year=2015 |issn=0959-4388 |doi=10.1016/j.conb.2015.06.012 |pages=74–79|pmid=26186237 |s2cid=31682363 }}</ref> In laboratory experiments, octopuses can readily be trained to distinguish between different shapes and patterns. They have been reported to practise [[observational learning]],<ref>{{cite news |url=http://news.bbc.co.uk/2/hi/europe/2796607.stm |title=Octopus intelligence: Jar opening |work=BBC News |date=25 February 2003 |access-date=4 February 2014}}</ref> although the validity of these findings is contested.<ref name="doug"/>  The [[veined octopus]] collects discarded [[coconut]] shells, then uses them to build a shelter, an example of [[tool use by animals|tool use]].<ref name=Finn>{{Cite journal |pmid=20064403 |year=2009 |last1=Finn |first1=J. K. |title=Defensive tool use in a coconut-carrying octopus |journal=Current Biology |volume=19 |issue=23 |pages=R1069–70 |last2=Tregenza |first2=T. |last3=Norman |first3=M. D. |doi=10.1016/j.cub.2009.10.052|s2cid=26835945 |doi-access=free |bibcode=2009CBio...19R1069F }}</ref> Octopuses have also been observed in what has been described as [[play (animal behaviour)|play]]: including moving around a bottle by jetting water at it.<ref>{{cite web |last1=Mather |first1=J. A. |last2=Anderson |first2=R. C. |year=1998 |title=What behavior can we expect of octopuses? |website=The Cephalopod Page |editor1-last=Wood |editor1-first=J. B. |url=http://www.thecephalopodpage.org/behavior.php |access-date=22 October 2006 |archive-date=5 October 2017 |archive-url=https://web.archive.org/web/20171005135515/http://www.thecephalopodpage.org/behavior.php |url-status=dead }}</ref> Octopuses often break out of aquariums and sometimes into others in search of food.<ref name="Wood Anderson">{{cite journal |url=http://www.thecephalopodpage.org/_pdf/2004Escape.pdf |title=Interspecific Evaluation of Octopus Escape Behavior |date=2004 |journal=Journal of Applied Animal Welfare Science |pages=95–106 |volume=7 |number=2 |access-date=11 September 2015 |doi=10.1207/s15327604jaws0702_2 |pmid=15234886 |last1=Wood |first1=J. B |last2=Anderson |first2=R. C |citeseerx=10.1.1.552.5888 |s2cid=16639444 }}</ref><ref>{{cite book |chapter-url={{google books |plainurl=y |id=lD8DAAAAQAAJ |page=38}} |title=Aquarium Notes – The Octopus; or, the "devil-fish" of fiction and of fact |last=Lee |first=Henry |chapter=V: The octopus out of water |date=1875 |publisher=Chapman and Hall |oclc=1544491 |location=London |access-date=11 September 2015 |pages=38–39 |quote=The marauding rascal had occasionally issued from the water in his tank, and clambered up the rocks, and over the wall into the next one; there he had helped himself to a young lump-fish, and, having devoured it, returned demurely to his own quarters by the same route, with well-filled stomach and contented mind.}}</ref><ref>{{Cite news |url= https://www.theguardian.com/world/2016/apr/13/the-great-escape-inky-the-octopus-legs-it-to-freedom-from-new-zealand-aquarium?CMP=Share_iOSApp_Other |title=The great escape: Inky the octopus legs it to freedom from aquarium |last=Ainge Roy |first=Eleanor |date=14 April 2016 |work=The Guardian (Australia)}}</ref> Evidence indicates that octopuses have [[sentience]] and can feel [[Pain in animals|pain]].<ref>{{Cite web |last=Henriques |first=Martha |date=25 July 2022 |title=The mysterious inner life of the octopus |url=https://www.bbc.com/future/article/20220720-do-octopuses-feel-pain |access-date=2024-07-29 |website=BBC |language=en-GB}}</ref>

===Camouflage and colour change===
[[File:Octopus.ogv| thumb|Video of ''Octopus cyanea'' moving and changing its colour, shape, and texture|alt=A video of an octopus changing its appearance]]

Octopuses use [[camouflage]] to hunt and to avoid predators. To do this, they use specialised skin cells that change colour. [[Chromatophore]]s contain yellow, orange, red, brown, or black pigments; most species have three of these colours, while some have two or four. Other colour-changing cells are reflective iridophores and white leucophores.<ref>{{cite web |url=http://www.docdatabase.net/more-tales-from-the-cryptic-the-common-atlantic-octopus-octopus-vulgaris-13832.html |title=Tales from the Cryptic: The Common Atlantic Octopus |access-date=27 July 2006 |last=Meyers |first=Nadia |publisher=Southeastern Regional Taxonomic Centre |archive-date=5 March 2022 |archive-url=https://web.archive.org/web/20220305152911/http://www.docdatabase.net/more-tales-from-the-cryptic-the-common-atlantic-octopus-octopus-vulgaris-13832.html |url-status=dead }}</ref> This colour-changing ability is also used to communicate with or warn other octopuses.<ref name=Mather/>{{rp|90–97}} The energy cost of the complete activation of the chromatophore system is high, nearly matching the energy used at rest.<ref>{{Cite journal |last1=Sonner |first1=Sofie C. |last2=Onthank |first2=Kirt L. |date=2024 |title=High energetic cost of color change in octopuses |journal=Proceedings of the National Academy of Sciences |language=en |volume=121 |issue=48 |pages=e2408386121 |doi=10.1073/pnas.2408386121 |pmid=39556731 |pmc=11621519 |bibcode=2024PNAS..12108386S |issn=0027-8424}}</ref>

Octopuses can create distracting patterns with waves of dark colouration across the body, a display known as the "passing cloud". Muscles in the skin change the texture of the mantle to achieve greater camouflage. In some species, the mantle can take on the bumpy appearance of algae-covered rocks. Diurnal, shallow water octopuses have more complex skin than their nocturnal and deep-sea counterparts. In the latter species, skin anatomy is limited to one colour or pattern.<ref name=Mather/>{{rp|89–97}}

Octopus' "moving rock" trick involves mimicking a rock and then inching across the open space with a speed matching that of the surrounding water.<ref>{{cite book |title=Cephalopod Behaviour |publisher=Cambridge University Press |last1=Hanlon |first1=R. T. |last2=Messenger |first2=J. B. |year=2018|pages=110–111|edition=2nd |isbn=978-0521897853}}</ref>

===Defence===
[[File:Hapalochlaena lunulata2.JPG|thumb|left|upright|[[Aposematism|Warning display]] of [[greater blue-ringed octopus]] (''Hapalochlaena lunulata'')|alt=An octopus among coral displaying conspicuous rings of turquoise outlined in black against a sandy background]]

Aside from humans, octopuses are prey for fishes, [[seabird]]s, [[sea otter]]s, [[pinniped]]s, [[cetacea]]ns, other cephalopods, and humans.<ref name=Crowfootdefense/> Octopuses typically hide or disguise themselves by camouflage and [[mimicry]]; some have conspicuous [[aposematism|warning coloration (aposematism)]] or [[deimatic behaviour<!--British English-->]] (“bluffing” a threatening appearance).<ref name=Mather/>{{rp|90–97}} An octopus may hide in their dens for as much as 40% of the day. When the octopus is approached, it may reach out an arm to investigate. 66% of ''[[Giant Pacific octopus|E. dofleini]]'' in one study had scars, with 50% missing arms.<ref name=Crowfootdefense>{{cite web |url=http://www.asnailsodyssey.com/LEARNABOUT/OCTOPUS/octoPred.php |title=Octopuses and Relatives: Predators and Defenses |last=Carefoot |first=Thomas |work=A Snail's Odyssey |access-date=13 April 2017 |archive-url=https://web.archive.org/web/20170421151656/http://www.asnailsodyssey.com/LEARNABOUT/OCTOPUS/octoPred.php |archive-date=21 April 2017 |url-status=dead }}</ref> The blue rings of the venomous blue-ringed octopus are hidden in muscular skin folds which contract when the animal is threatened, revealing the iridescent warning.<ref>{{cite journal |last1=Mäthger |first1=L. M. |last2=Bell |first2=G. R. |last3=Kuzirian |first3=A. M. |last4=Allen |first4=J. J. |last5=Hanlon |first5=R. T. |year=2012 |title=How does the blue-ringed octopus (''Hapalochlaena lunulata'') flash its blue rings? |journal=Journal of Experimental Biology |volume=215 |issue=21 |pages=3752–3757 |doi=10.1242/jeb.076869 |pmid=23053367 |doi-access=free |bibcode=2012JExpB.215.3752M }}</ref> The [[Atlantic white-spotted octopus]] (''Callistoctopus macropus'') becomes redder with bright white spots in a [[deimatic behaviour|deimatic display]]. Displays are often reinforced by stretching out the animal's arms, fins or web to make it look as big and threatening as possible.<ref name=Hanlon/>{{rp|80–81}}

Octopus try to escape from a predator by ejecting an ink cloud, which acts as a "smoke-screen" or a [[Pseudomorph#In other fields|decoy]], as well as to interfere with the attacker's sense of smell.<ref>{{Cite journal |last1=Caldwell |first1=R. L. |year=2005 |title=An Observation of Inking Behavior Protecting Adult ''Octopus bocki'' from Predation by Green Turtle (''Chelonia mydas'') Hatchlings |journal=Pacific Science |volume=59 |issue=1 |pages=69–72 |doi=10.1353/psc.2005.0004 |url=http://scholarspace.manoa.hawaii.edu/bitstream/10125/24161/1/PacSci_069_072.pdf |hdl=10125/24161 |s2cid=54223984 |hdl-access=free }}</ref> When severed by a predator, some octopuses can [[autotomy|detach their arm]],<ref name=Hanlon/>{{rp|86–87}} which can [[limb regeneration|grow back]].<ref name=Mather/>{{rp|85}} Some octopuses, such as the [[mimic octopus]], can combine their flexible bodies with their colour-changing ability to mimic other, more dangerous animals, such as [[Pterois|lionfish]], sea snakes, and [[eel]]s.<ref>{{cite journal |last1=Norman |first1=M. D. |last2=Finn |first2=J. |last3=Tregenza |first3=T. |title=Dynamic mimicry in an Indo-Malayan octopus |journal=Proceedings of the Royal Society |volume=268 |issue=1478 |pages=1755–8 |date=2001 |pmid=11522192 |pmc=1088805 |doi=10.1098/rspb.2001.1708 |url=http://marinebio.org/upload/files/mimic.pdf |access-date=1 October 2008 |archive-url=https://web.archive.org/web/20120210191131/http://marinebio.org/upload/files/mimic.pdf |archive-date=10 February 2012 |url-status=dead |df=dmy-all }}</ref><ref>{{cite journal |last=Norman |first=M. D. |year=2005 |title=The 'Mimic Octopus' (''Thaumoctopus mimicus'' n. gen. et sp.), a new octopus from the tropical Indo-West Pacific (Cephalopoda: Octopodidae) |url=http://www.mapress.com/mr/content/v25/2005f/n2p070.htm |journal=Molluscan Research |volume=25 |issue=2 |pages=57–70 |doi=10.11646/mr.25.2.1 |s2cid=260016769 }}</ref>

===Pathogens and parasites===
Cephalopods are known to be the intermediate or final [[host (biology)|hosts]] of various parasitic [[Cestoda|cestodes]], [[nematode]]s and copepods; 150 species of [[protist]]an and [[metazoa]]n parasites are recognised.<ref>{{cite journal |last1=Pascal |first1=Santiago |last2=Gestal |first2=Camino |last3=Estevez |first3=J. |last4=Arias |first4=Christian Andrés |year=1996 |title=Parasites in commercially-exploited cephalopods (Mollusca, Cephalopoda) in Spain: An updated perspective |journal=Aquaculture |volume=142 |issue=1–2 |pages=1–10 |doi=10.1016/0044-8486(96)01254-9 |bibcode=1996Aquac.142....1P }}</ref> The [[Dicyemidae]] are a family of tiny worms found in the renal appendages of many species;<ref>{{cite journal |last1=Furuya |first1=Hidetaka |last2=Tsuneki |first2=Kazuhiko |date=2003 |title=Biology of Dicyemid Mesozoans |journal=Zoological Science |volume=20 |issue=5 |pages=519–532 |doi=10.2108/zsj.20.519 |pmid=12777824|s2cid=29839345 |doi-access=free }}</ref> it is unclear whether they are parasitic or [[endosymbiont]]s. [[Coccidia]]ns in the genus ''[[Aggregata]]'' living in the gut cause serious illness in the host. Octopuses have an [[innate immune system]]; their [[hemocyte (invertebrate immune system cell)|haemocytes]] locate the foreign invader and attack it via [[phagocytosis]], encapsulation, infiltration, or [[cytotoxicity]]. The haemocytes also contribute to healing injures.<ref>{{cite journal |last1=Castellanos-Martínez |first1=Sheila |last2=Gestal |first2=Camino |year=2013 |title=Pathogens and immune response of cephalopods |journal=Journal of Experimental Marine Biology and Ecology |volume=447 |pages=14–22 |url=https://www.academia.edu/6443538 |doi=10.1016/j.jembe.2013.02.007 |bibcode=2013JEMBE.447...14C }}</ref> A gram-negative bacterium, ''[[Vibrio lentus]]'', can cause skin lesions, exposure of muscle and sometimes death.<ref>{{cite journal |last1=Farto |first1=R. |last2=Armada |first2=S. P. |last3=Montes |first3=M. |last4=Guisande |first4=J. A. |last5=Pérez |first5=M. J. |last6=Nieto |first6=T. P. |year=2003 |title=''Vibrio lentus'' associated with diseased wild octopus (''Octopus vulgaris'') |journal=Journal of Invertebrate Pathology |volume=83 |issue=2 |pages=149–156 |doi=10.1016/S0022-2011(03)00067-3|pmid=12788284 |bibcode=2003JInvP..83..149F }}</ref>